CVE-2020-27950: Apple iPadOS Information Disclosure Flaw

CVE-2020-27950 Overview

CVE-2020-27950 is a memory initialization vulnerability affecting multiple Apple operating systems including macOS, iOS, iPadOS, and watchOS. The flaw exists in the XNU kernel's handling of Mach message trailers, where improper memory initialization allows a malicious application to disclose sensitive kernel memory contents. This vulnerability has been confirmed as actively exploited in the wild and is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog.

Critical Impact

A malicious application may be able to disclose kernel memory, potentially exposing sensitive system information including cryptographic keys, memory addresses useful for bypassing ASLR, and other privileged data structures.

Affected Products

• Apple macOS (Big Sur 11.0.1, Catalina 10.15.7, High Sierra, Mojave)
• Apple iOS and iPadOS (versions prior to 14.2 and 12.4.9)
• Apple watchOS (versions prior to 7.1, 6.2.9, and 5.3.9)

Discovery Timeline

• 2020-12-08 - CVE-2020-27950 published to NVD
• 2025-10-27 - Last updated in NVD database

Technical Details for CVE-2020-27950

Vulnerability Analysis

This vulnerability stems from a memory initialization flaw in Apple's XNU kernel, specifically within the Mach message trailer handling subsystem. The XNU kernel's inter-process communication (IPC) mechanism relies on Mach messages, which include trailer structures containing metadata about the message. When these trailer structures are not properly initialized before use, residual kernel memory contents can leak to userspace applications.

The vulnerability is classified under CWE-665 (Improper Initialization), indicating that the kernel fails to properly initialize memory buffers before they are returned to requesting processes. An attacker with local access can craft specific Mach messages that trigger the disclosure of uninitialized kernel memory, potentially revealing sensitive information such as kernel pointers, cryptographic material, or other privileged data structures.

Root Cause

The root cause is improper memory initialization in the XNU kernel's Mach message handling code. When processing certain Mach message operations, the kernel allocates memory for message trailers but fails to zero-initialize the buffer before populating it with data. This leaves portions of the buffer containing residual kernel memory contents that are subsequently returned to the calling application.

Attack Vector

The attack requires local access to the target system, where a malicious application executes with standard user privileges. The attacker crafts Mach messages designed to trigger the vulnerable code path, causing the kernel to return trailer structures containing uninitialized memory. By repeatedly triggering this behavior and analyzing the returned data, an attacker can harvest sensitive kernel information.

The disclosed memory can be leveraged as part of a larger exploit chain—for example, defeating kernel address space layout randomization (KASLR) to enable subsequent kernel exploitation. According to the Packet Storm Security disclosure, this vulnerability was exploited alongside other flaws in real-world attacks.

Detection Methods for CVE-2020-27950

Indicators of Compromise

• Unusual patterns of Mach message activity from non-system applications
• Applications repeatedly requesting kernel IPC operations with abnormal trailer configurations
• Presence of known malicious applications associated with exploitation of this vulnerability
• Unexpected memory access patterns in system logs indicating kernel information disclosure attempts

Detection Strategies

• Monitor for applications making high volumes of Mach port operations, particularly those involving message trailer inspection
• Implement endpoint detection rules that identify known exploit signatures associated with XNU kernel vulnerabilities
• Deploy behavioral analysis to detect applications exhibiting suspicious IPC patterns characteristic of information disclosure attacks
• Leverage SentinelOne's kernel-level visibility to identify anomalous Mach message operations

Monitoring Recommendations

• Enable comprehensive system logging on macOS endpoints to capture Mach subsystem activity
• Utilize SentinelOne Singularity Platform for real-time monitoring of kernel-level operations across Apple devices
• Review application behavior for unauthorized attempts to access kernel memory through IPC mechanisms
• Maintain awareness of threat intelligence feeds for indicators related to active exploitation campaigns

How to Mitigate CVE-2020-27950

Immediate Actions Required

• Update all affected Apple devices to the patched versions immediately, as this vulnerability is actively exploited
• Prioritize patching for macOS Big Sur 11.0.1, iOS 14.2, iPadOS 14.2, and watchOS 7.1 or later
• For legacy devices, apply iOS 12.4.9, watchOS 6.2.9, or watchOS 5.3.9 as appropriate
• Review endpoint security configurations to ensure SentinelOne agents are deployed with kernel protection enabled

Patch Information

Apple has released security updates addressing this vulnerability across all affected platforms. The following updates contain the fix:

• macOS Big Sur 11.0.1 - Apple Security Advisory HT211931
• macOS Catalina 10.15.7 Supplemental Update - Apple Security Advisory HT211947
• Security Update 2020-006 for High Sierra and Mojave - Apple Security Advisory HT211946
• iOS 14.2 and iPadOS 14.2 - Apple Security Advisory HT211929
• iOS 12.4.9 - Apple Security Advisory HT211940
• watchOS 7.1 - Apple Security Advisory HT211928
• watchOS 6.2.9 - Apple Security Advisory HT211944
• watchOS 5.3.9 - Apple Security Advisory HT211945

This vulnerability is tracked in the CISA Known Exploited Vulnerabilities Catalog, and federal agencies are required to apply patches according to CISA's binding operational directives.

Workarounds

• Restrict installation of applications to trusted sources only (App Store) to reduce risk of malicious application deployment
• Implement application allowlisting to prevent unauthorized software from executing
• Deploy SentinelOne endpoint protection to detect and block exploitation attempts before kernel memory disclosure occurs
• Enforce mobile device management (MDM) policies requiring devices to maintain current OS versions

# Verify macOS version to confirm patch status
sw_vers -productVersion

# Check iOS/iPadOS version via MDM query or Settings > General > About
# Ensure version is 14.2+ or 12.4.9+ depending on device generation

# List installed security updates on macOS
softwareupdate --history